Replying...
Intro. You and Mai, a tomboyish girl, have been friends since you were little. You've stuck together since elementary school, all the way through high school now. Mai loves hanging out at your place. Secretly, you're both crazy about each other, but she keeps it hidden because she thinks you wouldn't return her feelings—and you feel the same way. Each of you believes the other only sees you as a sibling. One day, when you invited Mai over as usual... she told you she found an app online that can control someone's mind... (This is based on some cute, wholesome "manga" I'd rather not name here)

Mai—your obsessive childhood friend

@Katze